The present invention relates generally to an apparatus for winding torsion springs and, in particular, to an apparatus for counterbalancing an overhead door with a torsion spring.
Torsion spring counterbalance assemblies are commonly utilized to counterbalance the weight of an overhead door such as a garage door. Most residential and commercial overhead garage doors are of the sectional type which are suspended on overhead tracks when the door is in the up position. A typical torsion spring counterbalance assembly includes a shaft which is journaled for rotation in two or more bearing mounts which are generally attached to the wall above the door opening such that the shaft extends generally horizontally parallel with the door lintel. Cable drums are secured on each end of the shaft and each drum is attached to one end of an associated cable which is wound about the drum and has its opposite end secured to the bottom panel or section of the garage door. The shaft extends through the center of a coiled counterbalance torsion spring having one end secured to the shaft by a winding plug and the other end secured to the door lintel by an anchor plug. The spring is pretensioned and releasably attached to the shaft by the winding plug. The pretensioning tends to urge the drums to rotate in the take-up direction. As the door is lowered from its overhead position, its weight is increasingly shifted from the overhead tracks to the cables. This weight is counterbalanced by the torsion spring which is being wound tighter through the cable drums and the shaft.
Typically, the cable drums, the winding plug and the anchor plug are formed from metal castings. Since larger diameter springs are required for heavier doors, several different sets of spring winding and anchor plugs must be utilized in order to match each different diameter torsion spring. Thus, the manufacturer must provide separate molds for the different size plugs and provide a different production run for each size plug. The distributor and the garage door installer must carry a stock of each of the different size plugs to fulfill the demands of the marketplace.
It is an object of the present invention to provide an apparatus for counterbalancing an overhead door which apparatus accommodates various diameters of torsion springs.
It is another object of the present invention to provide an apparatus for counterbalancing an overhead door which apparatus reduces the need of the manufacturer to provide and the distributor and installer to stock many different sizes of torsion spring winding and anchor plugs.